Strava v Garmin connect
- Thread starter Andy_G
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jdtate101
Ex-Fatman
- Location
- Boring Birmingham
Neither will be accurate as far as calories burnt, they are both an approximation based upon mathematical formula (speed, distance, HR etc). For example you will notice when you freewheel down a big hill the calorie counter on your Garmin will still climb.
This will provide more more background for you:
http://www.dcrainmaker.com/2010/11/how-calorie-measurement-works-on-garmin.html
This will provide more more background for you:
http://www.dcrainmaker.com/2010/11/how-calorie-measurement-works-on-garmin.html
lulubel
Über Member
- Location
- Malaga, Spain
Of course it will. Your heart doesn't stop beating, and your CV system doesn't stop working just because you're not turning the pedals.
jdtate101
Ex-Fatman
- Location
- Boring Birmingham
Yes of course, but it's inaccurate in the way it measures your effort. Another example is using a turbo trainer. If you use a turbo with your garmin with the GPS turned off but have a speed/cadance pod attached it will record your speed. Holding 20mph on the turbo takes significant effort, but it much easier on the road (flat), yet they still record as the same level of calories. This is one of the reasons why powermeters are used for professional training, it's a direct measurement of effort at any given time.
lulubel
Über Member
- Location
- Malaga, Spain
I thought we were talking about heart rate, not distance/speed.
Anyway, while I appreciate that a power meter will allow you to calculate the energy required to move the bike, I've argued before (and even quoted the laws of thermodynamics to back up my argument) that it doesn't tell the whole story of what the body is doing, so a power meter can't be used to calculate calories burned accurately either. As far as I understand it, professionals use power meters (in conjunction with HRMs) because they're trying to increase their power output for a given heart rate, not to tell them how much they can eat.
To answer the OP, none of the available methods of calculating calories burned is accurate. The calories to maintain your body weight that whatever website you're using has given you aren't accurate either - they're based on averages. You need to experiment with the different options, and figure out which estimates come closest for you.
jdtate101
Ex-Fatman
- Location
- Boring Birmingham
I think we are talking cross purposes. I agree HR is a key component in calorie calculation, but most Garmin units use a component of speed/distance to work out how much "effort" is involved. Of course this doesn't take gradient etc.. into account, but it could be argued that your HR will be at the same level if you are going slowly up a steep hill vs going hell for leather on the flat, so energy burnt should be roughly equal(ish).
Basically any calculations these unit/websites make will be inaccurate as they really need to biological baseline personal to each user in order to get more accuracy (Leaf Test / VO2 MAX). My observation about Powermeters was just that it's a direct measurement of output, not an approximation by mathematical formula, thus tends to be trusted more as a measure of how much somebody has worked over a given ride.
Basically any calculations these unit/websites make will be inaccurate as they really need to biological baseline personal to each user in order to get more accuracy (Leaf Test / VO2 MAX). My observation about Powermeters was just that it's a direct measurement of output, not an approximation by mathematical formula, thus tends to be trusted more as a measure of how much somebody has worked over a given ride.
amaferanga
Veteran
- Location
- Bolton
A power meter can be used to give a very good approximation of calories burnt. It'll tell you the amount of work you're doing to move the bike, which when you're riding a bike is where the vast majority of your energy is going. Combine the kJ figure with your matabolic (?) efficiency and you get a calorie figure. Fortunately the efficiency doesn't vary much between individuals and for an individual varies even less (with age, fitness, etc.) and assuming ~25% efficiency so you get a 1:1 relationship between calories and kJ keeps it simple and within around +/-10% accuracy for most people. Clearly the calorie figure doesn't include the calories burnt just to stay alive, but you can estimate that fairly easily and it's much smaller than the work being done to propel the bike anyway.
HR on the other hand tells you how fast your heart is beating. The work required that leads to a given HR is a complete unknown and quite clearly two people could have an identical HR from doing very different amounts of work. So you then have to make up formulae that may be reasonably good approximations for some people, but will be wildly inaccurate for others.
So forget about thermodynamics - calorie estimates based on power meter data are better than HR-based guesses.
